Building and keeping track of a life list is really fun IMO

it's not for everyone, but if you are a numbers/data person, or want to better remember every cool thing you see, or (as is especially true for me) you use gaps as a motivation to get out and see new places and look for new creatures - a life list is a great way to scratch those itches.
I keep my lifelist as an Excel spreadsheet, with seperate tabs for fishes, birds, herpetiles, mammals and invertebrates. Within each sheet, order and family level taxa are sorted by some semblance of taxonomic order, and species within each family are arranged in alphabetic order of scientific name
This is exactly my method too - Excel spreadsheet, separate tab for each class, animals sorted by order and family within each tab, and species listed in alphabetic order by Latin name. I also have columns with my species totals - for family, order and class.
I have a column where I list every single zoo where I know I saw that species, and then additionally a column with the total number of zoos. I don't organize by individual visits - mainly because there are a few zoos that I've been local to and couldn't begin to count how many times I saw something there.
For anyone starting a life list, I can't recommend enough using a spreadsheet program like Excel or Google Sheets - they are designed for large amounts of information like this, and it's very easy to add or delete entries as well as adding up totals. I use Word documents more for straight one-time lists, like my annual bird count or species lists for individual zoos.
and a checkbox for species seen in the wild or “domestic” settings (pets, pet stores, farms, basically any non-wild and non-zoo setting).
I keep separate spreadsheets for captive and wild species I've seen, but I do use color-coding in my spreadsheets to show where there is overlap. For my wild life list, I also keep track of each year I see or don't see a species.
Subspecies are inconsistently tracked as indented lines under their species.
Subspecies is one thing I haven't made much of an effort to track. When I do happen to know subspecies information, I will usually just add it as a note into the column where I track each zoo - Red Pandas for example:
Blank Park, Charles Paddock, Knoxville, Oklahoma City, Philadelphia, Sacramento, Scovill, St Louis (Nepalese); Asheville NC, Greensboro, Nashville, San Diego Zoo (Chinese); Memphis (unknown)
The other issue I have is that, at a certain point, there are too many columns to easily view everything without having to side-scroll.
It was a ton of work to get set up like that, took me a couple months working on it a few hours a day.
And this is why I have not sorted my photographs by species at all

I made an attempt and abandoned it within a couple days as I realized the sheer number of photos I would have to sort through.